We use classical immunogenetic techniques as well as techniques of molecular biology to study the genetics of rabbit immunoglobulins (Igs) and T cell receptors and the regulated expression of the genes that encode these molecules. A rabbit cDNA copy of splenic mRNA is spliced to C mu from a site 635 bp 3' of the conserved octanucleotide of the heavy chain enhancer. A splice site is present at a similar position in the intron sequences of mouse and man. There is evidence that such spliced steril transcripts occur in developing B cells of mice and in some human cell lines. The evolutionary conservation of the spliced mRNA in these three species suggest that it may play a functional role during B cell ontogeny. We are characterizing T cell receptor C beta genes from rabbits which have three copies of the C beta constant region. We previously demonstrated that there are allotypes of rabbit C beta1. We have now sequenced about 4 kb of cloned 6 kb fragment from an animal of type b and demonstrated that this fragment contains a rabbit C beta2 gene. Comparisons with the cDNA sequence from an animal of C beta type a show replacement changes in the first and third exons thus demonstrating that there are also allotypic forms of C beta2. Decreased galactosylation of IgG that is observed in a sera of rheumatoid patients is also observed in the IgG prepared from sera of rabbits post-immunization with Streptococcal vaccines. Therefore the difference in IgG galactosylation seen in patients may also be induced rather than reflect an inherent genetic difference in individuals with rheumatoid disease.